The present invention relates generally to a biological agent detector including two detecting devices that each alternate between a sample collection mode and a sample analysis mode to provide continuous aerosol collection and air monitoring for biological agents.
As an example biological agent detector, a Chemical Biological Mass Spectrometer Block II (CBMS II) detects biological agents present in the air by employing a two-step process using a detector including a pyrolyzer and an associated mass spectrometer. During sample collection, a first pump draws 330 liters of air per minute into an inlet of a bio-concentrator. The bio-concentrator extracts aerosol particles that are drawn into the pyrolyzer by a second pump at 1 liter per minute. The aerosol drawn into the pyrolyzer includes secondary particles, such as dust, fibers, and dirt, and may also include biological agents, such as anthrax or other biowarfare agents. A sample of the aerosol collects at the bottom of a pyrotube in the pyrolyzer. The air and aerosol particles not collected in the pyrotube are exhausted through an exhaust outlet.
During sample analysis, the aerosol sample collected at the bottom of the pyrotube is analyzed to identify any biological agents in the air. A small droplet of a methylating reagent, such as tetramethylammonium hydroxide (TMAH) dissolved in methanol, is added to the air sample with a hypodermic needle. The hypodermic needle is typically made of stainless steel. If the sample includes any biological agents, the methylating reagent derivatizes organic materials to make them more volatile. For example, fatty acids in the cell walls of the bacterial agents form Fatty Acid Methylated Esters (FAMEs).
The sample in the pyrotube is then rapidly heated or pyrolyzed to form gas molecules during an analysis phase. A third pump draws 1 milliliter per second into the mass spectrometer for identification of any biological agents. Biological agents have distinctive patterns of organic molecules. If any biological agents are present in the sample, the mass spectrometer identifies the biological agents by determining the molecular pattern. After a molecular pattern is determined, the pattern is compared to a pre-programmed list of patterns for identification of any biological agents in the air sample.
A drawback to the prior art biological agent detector is that the prior art system must stop collection of an aerosol sample in the pyrotube during the analysis phase, and therefore does not detect any biological agents present in the air during sample analysis. Therefore, the sample collection is intermittent, with time gaps in which no air monitoring occurs. This increases the time required to detect the presence of any biological agents and in some situations may result in a failure to detect a transient agent.
To provide continuous detection and analysis, a second pyrolyzer and bio-concentrator are needed. However, duplicating the bio-concentrator and the pyrolyzer is expensive.
Thus, it is desirable to have a biological agent detector including two detecting devices that share a bio-concentrator and that each alternate between a sample collection mode and a sample analysis mode to provide continuous collection and monitoring of an air sample, as well as overcoming the other above-mentioned deficiencies of the prior art.